Ammonium nitrate disks



Dec. 13, 1966 J. J. YANCIK AMMONIUM NITRATE DISKS Filed April 10, 1964 FIGURE 11 INVENTOR JOSEPH J. YANCIK BY L :g /AL V TTORNEY atent 3,291,659 Patented Dec. 13, 1966 fice 3,291,659 AMMDNIUM NlTRATE DISKS Joseph J. Yancik, Florissant, Mo, assignor to Monsanto Company, St. Louis, Mo, a corporation of Delaware Filed Apr. 10, 1964, Ser. No. 358,862 11 Claims. (Q1. 149-4) This invention relates to ammonium nitrate having unique characteristics, and to blasting agents and explosives containing such material.

Ammonium nitrate has been used extensively in blasting agents and explosives for many years. Although this material is a relatively strong oxidizing agent, it is not readily detonatable. Therefore, ammonium nitrate blasting agents or explosive compositions usually contain this material in uniform intimate Contact with various fuels, modifiers and sensitizers which in themselves are either explosive or non-explosive. Recently, fertilizer grade ammonium nitrate has enjoyed Widespread usage in the explosive field. This material in the form of prills or solidified droplets is conventionally mixed with a liquid hydrocarbonaceous fuel, such as fuel oil, in the preparation of substantially oxygen balanced blasting agents. The regular grades of fertilizer grade ammonium nitrate prills are porous and have a particle density up to about 1.45. Other commercially available types of fertilizer grade ammonium nitrate prills are hard, smooth, relatively non-porous and have a particle density in the neighborhood of 1.51.6 or more. In spite of the recognized advantages that should result from using high density prills for the formulation of correspondingly dense blasting agents or explosives, the hard ammonium nitrate prills are not suitable components of explosive compositions. Their smooth, practically imperforate surfaces militate against the requisite intimate contact between the ammonium nitrate and the other constituents of the explosive mixtures. Thus explosive compositions based thereon are inordinately difficult to initiate and are not self propagating. Previous attempts to utilize high density ammonium nitrate prills in explosive compositions have centered about grinding or comminution of the prills, and using the ground material in explosive formulations. While this provides a source of high density ammonium nitrate for incorporation into explosives, some additional provision must be made to obtain intimate contact between ammonium nitrate and the other components. The requisite intimate contact has been previously achieved by the incorporation of porous ammonium nitrate into the blends, or by grinding the ammonium nitrate in the presence of the fuels and the like. These methods, while generally satisfactory, dilute the advantages of using dense ammonium nitrate or rely on the inherently hazardous physical working of an explosive composition. Thus, prior to the advent of the present invention, the utilization of dense ammonium nitrate prills in blasting agents or explosives had serious inherent shortcomings.

It is, therefore, an object of the invention to provide dense ammonium nitrate explosives and blasting agents overcoming the disadvantages of the prior art. A more specific object is to provide granular ammonium nitrate in a new and novel physical form, and a method of making the same. Another object is to provide improved explosives and blasting agents.

These and other objects are accomplished in accordance with the present invention, generally speaking, by subjecting hard, high density ammonium nitrate prills to pressure in one plane to reduce the dimension of the prills in that plane while increasing the dimensions of the prills in a plane substantially perpendicular to the applied force. In other words, high density ammonium nitrate prills are pressed or squeezed in one plane to form flattened ammonium nitrate particles having unique configurations and characteristics. While the requisite pressing or squeezing can be accomplished by positioning the high density prills between a pair of any rigid cooperating members, it is preferred to use rolls for this purpose. Thus, on a commercial scale, the high density prills are squeezed and pressed by passing them between a pair of rolls having a gap opening smaller than the diameter of the prills. The rolls must not be in contact with one another and it is essential that a measurable gap occurs between them. The magnitude of the gap is, of course, dependent upon the degree or the amount of pressing desired and also upon the particle size of the feed stock. In most instances it has been found necessary to maintain the gap at a value which is not greater than about one-half of the average median diameter of the material being passed through the rolls. For example, when using high density material in the screen size range of 8-20 mesh (U.S.S.) which corresponds to diameters between about 0.094 and about 0.033 inch, the gap between the rollers generally does not exceed about 0.03 inch or 30 mils. In most instances, however, the intensity of the pressing or squeezing is much more intense and for a feed stock of the above average size range the gap between the rollers is generally maintained between about 3 and 30 mils.

When a smooth set of rolls having a roller gap opening smaller than the diameter of the prill is thus employed, the extent of the pressing and squeezing of the prills is dependent upon a number of factors. These include (1) gap setting, (2) feed head pressure, (3) diameter of the rolls, (4) the speed of the rolls, (5) differential speeds between the rolls and (6) the original hardness and particle density of the feed material. Generally speaking, the amount of pressing increases with reduced gap setting, increased feed head pressure, increased roller diameter, decreasing rate of revolution and decreasing differential speeds between the rolls. Also the pressing action is intensified as the hardness or particle density of the feed material increases.

Smooth surfaced rolls are preferred in accordance with this invention but various other types of rolls can be employed with equal success. Products having an exceedingly wide range of explosive characteristics can be produced by rolls having other surface configurations. For example, the rolls may be provided with matting or waffie designs, corrugations and the like. In any event, the rolls employed must subject the prills to a squeezing or pressing action so as to reduce their dimension in one plane while increasing it in another.

The particulate ammonium nitrate thus obtained is in the form of substantially planar flakes or disks having unique physical structures and properties. Each rolled particle contains ammonium nitrate in a plurality of physical conditions. This novel form provides ammonium nitrate materials having a specific surface area which is inordinately great for the size range of the particles. The unusual configuration of the particles also results in a product having increased capillary attraction for liquid adjuvants.

The ammonium nitrate flakes or disks of the present invention have density gradients along their major axes. The granular ammonium nitrate of the present invention may also be defined as flakes or disks in each of which the physical condition of the ammonium nitrate changes gradually from the central to peripheral areas or regions. The central portion of each flake is a solid, unitary, dense mass, while the periphery of the flake is in the form of a cohesive lattice or network of ammonium nitrate particles. The lattice is relatively open at the edge of each disk and gradually assumes a tighter closed configuration as it approaches and merges with the dense central portion. The individual flakes or disks do not vary significantly in thickness between their central and peripheral portions. The area ratio of the dense central portion to the cohesive, fractured outer ring can vary considerably. It is only necessary that the dense central portion be surrounded in one plane by at least a narrow fringe of the fractured material.

The physical confirmation of the present ammonium nitrate disks is readily apparent by reference to the drawing in which FIGURE I is a frontal viewof a representative disk prepared in accordance with the present invention, and

FIGURE II is a cross-sectional view along the line IIII of FIGURE 1.

Presently available evidence indicates that the absolute density of all the ammonium nitrate in the flakes is substantially uniform. While the absolute density of ainmonium nitrate is apparently constant, the apparent particle density decreases as the distance from the central area of the flake increases. The present ammonium nitrate flakes have a particle density of about 1.7 in their central areas and the density approaches about 1.0 in the peripheral regions of the flakes. Because of their unique configuration, the present ammonium nitrate flakes or disks can have bulk densities considerably less than about 55 pounds per cubic foot and as low as about 45 or even 40 pounds per cubic foot. This is in contrast to a bulk density of about 60 pounds per cubic foot for dense ammonium nitrate prills in the 820 mesh (U.S.S.) size range.

The term absolute density as used herein is synonymous with specific gravity or crystalline density and is expressed in grams per cubic centimeter. Particle density and apparent particle density are use in their generally accepted sense to express the absolute density of the individual discrete particle. Bulk density is used to designate the weight of particulate material that can be confined in a given space while maintaining its original form and is conveniently expressed in pounds per cubic foot.

The rolling and pressing operation results in an extraordinary increase in the specific surface area of the ammonium nitrate prills being treated. This renders the treated prills much more amenable to oil absorption and detonation reaction. The magnitude in the increase of the specific surface area in the prills is phenomenal. This is brought out by a comparison of the specific surface areas of prilled ammonium nitrate in the 8-20 mesh size range (U.S.S.) before and after treatment. In accordance with the present invention by the seemingly simple expedient of rolling and pressing prills of this size, their specific surface area is increased from about 0002 square meter per gram to more than 30 square meters per gram. Thus, in the rolling operation, the specific surface area of the ammonium nitrate is increased about 15,000 times. Generally speaking, the ammonium nitrate flakes or disks have a major axis or dimension of at least about 30 mils. Therefore, they are sufiiciently large to be retained on a 25 mesh screen. The upper limit of the particle size is not particularly significant and can vary considerably because of ease of handling and other commercial considerations. However, it is generally preferred to utilize ammonium nitrate flakes or disks having a major dimension between about 75 mils and 500 mils and more specifically between about and about 400 mils. The specific surface area of the flaked ammonium nitrate within these ranges can vary according to the present invention between about 1 and 50 square meters per gram. This range of specific surface area is normally associated with granular or finely powdered materials having average particle diameters between about 0.18 and about 0.003 micron. When the specific surface area is less than unity, the advantageous characteristics of the present granular ammonium nitrate decrease rapidly. On the other hand, particles having specific surface areas greater than about 50 square meters per gram are exceedingly fragile and cannot readily survive the usual jarring and handling involved in transporting, mixing, formulating and the like. Therefore, for most commercial applications, it is generally preferred to utilize particles having specific surface areas between about 25 and about 35 square meters per gram.

The essential and unique prerequisite for optimum results is that the original feed material be substantially spherical in shape so as the spheres pass through the rollers, they are pressed to the great circle plane of the roller. Each prill, in passing through the roller, is compressed along one great circle and simultaneously spreads out parallel to the rolls since it is free to move in this plane. This lateral movement of the prill creates a particle which is highly compacted in the central area but has a cohesive, highly fractured ring of outer material. It is believed that this outer ring imparts the excellent detonation characteristics to the products because of the vast amount of readily available surface area. The flat flake-like particles thus formed have excellent cohesive strength and can be readily mixed and bandled in conventional equipment used in the production of blasting agents, explosive compositions, solid propellants, gas generating charges and the like. In spite of the inherent cohesive strength of the particles of this invention, a portion of them is fractured and broken down during the rolling and subsequent operating procedures. This partial disintegration of the flakes or disks results in the formation of some very finely divided, high density ammonium nitrate particles in the product being prepared. In most instances such a partial disintegration is advantageous because it tends to increase the bulk or packing density of the composition. However, excessive particle disintegration is generally not desirable so that the predominate portion of the ammonium nitrate prepared in accordance with the present invention is generally in the form of flakes having a density gradient.

Specific surface area is determined by the accepted nitrogen adsorption method described in A new method for measuring the surface areas of finely divided materials and for determining the size of particles by P. H. Emmett in Symposium on New Methods for Particle Size Determination in Sub-Sieve Range published by the American Society for Testing Materials, March, 1951, page 95. The value of 0.162 square millimicron for the area covered by one surface adsorbed nitrogen molecule is used in calculating the specific surface area.

The ammonium nitrate utilized as a feed material in accordance with the present invention must be in the form of dense, hard, substantially spherical prills. The hardness or crushing resistance of ammonium nitrate prills increases with the particle density of the ammonium nitrate. Thus, very dense ammonium nitrate prills are comparatively hard and quite crush resistant whereas the ordinary fertilizer grade is comparatively soft and easy to deform. The ammonium nitrate prills used in the present process must have a particle density of at least about 1.5. This type of prill is smooth, imperforate and relatively non-absorptive prior to the present treatment.

Any type of ammonium nitrate prills having the requisite particle density can be employed. For example, prills prepared in accordance with the teachings of U.S. 3,030,- 179, granted April 17, 1962 to McFarlin and Stites and having a density of about 1.65 are particularly well suited for the purposes of the present invention.

The ammonium nitrate utilized in the present invention need not be pure and in fact is advantageously stabilized or rendered anti-caking by the addition or incorporation of a wide variety of minor components. These include, for example, magnesium nitrate, calcium nitrate, sulfonated aromatic dyestuffs, alkyl aryl sulfonates, organic amines, clay, kaolin, bentonite, diatomaceous earth, talc and the like. In addition other modifying agents can be incorporated into coated on ammonium nitrate prillsprior to. pressing them in accordance with the present invention.

As pointed out above, the feed stock used in accordance with the present invention must be hard, high density prilled ammonium nitrate. Powders, elongated or irregular shaped feed particles tend to be extruded rather than squeezed or pressed which is an essential part of the process. Although such shaped particles can be used, the resultant product does not have as clearly de fined density gradient particles or the high specific surface areas. These types of feed products create excessive fines or are difhcult to convey, mix, and package. Likewise, regular porous low density ammonium nitrate prills are not generally adaptable to the process of the present invention. These prills are of a much softer nature and their rolling generally results in the formation of an extruded sheet-type product which must be subsequently broken up into individual particles.

Although untreated, high density ammonium nitrate prills are capable of holdim only from about 1% to 2% fuel oil on their surfaces, the exceedingly great available specific surface area of the disk or flake materials under consideration permits the absorption of well over fuel oil. The greatly increased specific surface area also insures intimate contact with any particulate solid additive. Thus, the ammonium nitrate particles of the present invention are particularly well suited for the preparation of ammonium nitrate-fuel blasting agents or nitrocarbonitrates. In preparing such blasting agents, particulate material from the rolls is mixed with the requisite amount of fuel to render the resulting composition substantially oxygen balanced. For example, the stoichiometric amount of fuel oil required is approximately 5.7% and in most instances about 6% fuel oil is employed to enhance the detonation characteristics of the resulting compositions. However, generally speaking the amount of fuel oil mixed with the ammonium nitrate can vary between about 4% and 10%, depending upon the explosive characteristics of the product. The mixing of the ammonium nitrate with fuel oil can be accomplished in any conventional manner. In any event it is essential that the fuel oil be mixed with the ammonium nitrate subsequent to the rolling operation. The addition of the fuel oil prior to rolling tends to soften the prills and minimizes the formation of newly available surface area.

While fuel oil, and particularly No. 2 fuel oil, is set forth above as a typical liquid fuel for compounding with ammonium nitrate, various other types of commercially available liquid hydrocarbons can be used instead. In fact, any liquid hydrocarbon that can be mixed in liquid form is suitable for the formulation of such blasting agents. These include diesel oil, kerosene, lube oil, coal oil and the like. It is only necessary that the fuel employed be readily combustible and capable of distribution over the ammonium nitrate surfaces while preferably having a flash point of at least 175 F.

The invention and the manner in which its objects are achieved will be more readily understood by reference to the following illustrative preferred embodiments thereof. In these examples and throughout the specification, all proportions are expressed in parts by weight unless otherwise indicated.

Example 1 A quantity of high density prilled ammonium nitrate prepared in accordance with U.S. 3,030,179, referred to above, was provided. This material contained about .5 magnesium nitrate and had a particle size range of about 8 to 20 mesh (U.S.S.). This material was pressed and compacted by passing it through a pair of rollers. The rollers employed were smooth, 8 inches in diameter and rotating at a speed of approximately 20 revolutions per minute. The space or gap opening between these rollers was approximately 5 mils, i.e., 0.005 inch. Since the 8 to 20 mesh size range of the feed product corresponds to a particle size between about 33 and 94 mils, the gap opening was approximately one-sixth of the diameter of the smallest particles and about onetwentieth of the largest diameter particle. Thus, in passing through the rolls, the dimensions of the prill in one plane were reduced accordingly. The rolls were maintained in a substantially horizontal position and the ammonium nitrate prills fed therethrough at a constant rate. The rate of feed was sufliciently slow so that the head feed pressure was practically negligible. In passing through the rolls, each of the prills was reduced to a flake or disk. These flakes were substantially circular and had a diameter of from about to 400 'mils. The diameter of the flaked product is substantially proportional to the diameter of the spherical feed material. The material issuing from the rolls is in the form of individually discrete flakes. While there is some slight tendency for these flakes to form clusters or platelets in passing through the rolls, this occurs only to a minor degree. Any platelets thus formed are quite small, fragile and readily broken up. The flakes thus formed Were collected in a suitable container and held for shipping or subsequent formulation. The product thus obtained had a bulk or packing density of about 40 pounds per cubic foot in contrast to a packing density of 60 pounds per cubic foot for the feed material. Likewise, the specific surface area of the rolled material was tremendously' increased. While the feed stock had a specific surface area of only about 20 square centimeters per gram, the flake material prepared in accordance with this example had a specific surface area of approximately 50 square meters per gram. Thus, by the simple expedient of rolling the hard, dense ammonium nitrate prills, the specific surface area of this material was increased more than 25,000 times.

Example 2 Ab out 94 parts of the flaked ammonium nitrate prepared in accordance with Example 1 was mixed in a concrete mixer with about 6 parts of No. 2 fuel oil. The mixing was continued for about 2 minutes at which time the fuel oil Was substantially completely adsorbed by the ammonium nitrate forming a free-flowing, uniform mixture of ammonium nitrate and fuel oil. This material as it was removed from the mixer had a bu k density of about 56 pounds per cubic foot. The blasting agent thus obtained was charged into a cylindrical iron pipe about 3 inches in diameter and about 48 inches long, and then vibrated to achieve maximum packing density. The vibrated packing or bulk density thus obtained was approximately 65 pounds per cubic foot. This material was readily initiated with a single No. 6 blasting cap, was self-propagating, and detonated at a rate of approximately 15,000 feet per second.

In accordance with the procedures of Examples 1 and 2, a series of blasting agents containing about 94% ammonium nitrate flaked in accordance with the present invention and about 6% fuel oil were prepared. Various modifications in the diameter and the speed of the rolls and the gap between the rolls were made in the preparation of the ammonium nitrate used. The blasting agents thus prepared were charged into iron pipes about 3 inches in diameter, vibrated and initiated in the manner described in connection with the preceding example. The results and 8 surface area do not in any Way arfect the availability of the internal surface area for absorption and for detonation reaction.

The ferrophosphorus and bran of the above examples 5 are used only for purposes of illustration. Other subthe explosive characteristics of these materials are set forth stances well known in the explosive field could be readily below. substituted to provide a final product which would per- TABLE I Roll Pouring Vibrated Detonation Ex. Din Gap Roll Density Density Velocity Initiator (In.) (Mil) (r.p.m.) (lbS./I1.fl7.) (Packaged) (feet/sec.)

(lbs/edit.)

8 20 30 a 67 15, 000 1 s 15 20 55 50 15,500 1 s 20 20 59 70 15,500 2 s 25 20 50 71 15, 000 5 s 30 20 51 72 15,000 8 8 35 20 02 72 14, 500 20 10 3 300 50 50 14,000 1 10 500 55 54 14, 000 1 10 15 55 as 15,000 2 10 15 300 55 66 14, 500 1 10 300 55 6s 15, 000 2 10 56 70 15, 500 3 10 25 s50 58 75 15, 000 15 1 300 Diff.

In the above examples, the speed of both rollers was form in a similar manner. For example, dense explosives the same with the exception of Examples 11 and 14. In having suitable detonation sensitivity can be prepared by these two examples one roller was rotating at about 300 incorporating ferrophos-phorus as well as lead, lead salts, r.p.m. and the other at about 330 r.p.m. to provide a differrosilicon, iron oxides and the like into formulations ferential of about r.p.m. The numerical value given 30 Containing the present flaked ammonium nitrate particles. under the heading Initiator represents the quantity of Likewise, the wheat bran of Example 18 can be replaced No. 6 blasting caps required to detonate reliably the ex- With other low density absorption materials, including plosive charge, corn meal, wheat flour, coal, carbon, rosin, soybean meal,

In order to illustrate the versatility of the pressed and bagasse and the like. The materials which are used to compacted ammonium nitrate of the present invention, an alter the density of the final product can usually be additional series of blasting agents were prepared and P n in mo n s 11p to ab ut 20% based on ammonium r t d i accordance ith th procedure of Examples 2-15. nitrate-fuel oil without having any significantly deleterious In these examples, flaked ammonium nitrate prepared in efi'ect on the detonation sensitivity of the composition. accordance with the general procedure of Example 12 \Vhen an explosive or blasting agent having less sensitivity above was mixed with fuel oil as well as a number of 40 a be employed, such modifiers can be present in signifiadditional modifying components and tested as described cantly larger quantities. above. The results of these tests are set forth below. Ann additional unique advantage ofiered by the flaked TABLE II ammonium nitrate of the present invention is illustrated by Example 19. By reference to this example, it will be vibrated noted that the density of the blasting agent was increased Ex. Additive (Packaged) Detonation Initiator, about 10% merely by adding about 2% water while sub- Veloclty caps stantially maintaining the high detonation rate. Such addition of water can be used in any instances in which the 5% 75 13, 000 3 ammonium nitrate is formulated with a substantially n"- 10% FYP 7s 12 000 3 anhydrous inorganic salt. The amount of water that can 2:: iii- 88 be added Without having any detrimental effect is dependent upon the amount of anhydrous additive originally In the above table the abbreviation FF is used to de In the ammoriium {litmta w using the type of Signate ferrophosphorus The other terms correspond dense ammonium nitrate employed 1n the above examples, with those used in Table I. up to about 2.5% of water based on the weight of ammo- The data of Table II based on weight percentage of P nitrate can be added It Is behev.ed that i Water AN-FO clearly shows that due to the unique structure of 1s chemlcany hald by the pun thus 18 not as the pressed and squeezed high density ammonium nitrate free water to dampen the explosive characterlstlcs of the prill the detonation sensitivity of the product is not greatly product affected by the addition of essentially inert materials any number of Water Smile ammqmum filtrate which are added primarily for purposes of densification bummg rate. Catalysts Could be dissolved m the Water or to produce a low density blasting agent before spraying onto the rolled product. Catalysts well Table II illustrates the effects of high and low density known In the Q such chromate Salts d1- additives. Ferrophosphorus greatly increases the density chromate.salts fernc.salts and the i p to promote of the product but has little, if any, efiect on the detomore urilform bumfng charactenstlcs' Although nation sensitivity when used in amounts as great as about h burmng process 15 not dlrecfly to the detona' 15% based on the Weight of the ammonium nitrate-fuel non P kfoth are known to be 'Speclfic surfaca area oil mixture The addition of Wheat bran to the Squeezed reactions. It is well recognlzed that the catalysts do not and pressed high density ammonium nitrate results in a lncfease [[116 mfpl'oswe Strength but l Promote {more low density product Here again in spite of the large uniform explos1ve strength and exploslve characteristics. volume of filler, the detonation sensitivity is only slightly In h interest of Clarity, the advantages of the Presfint altered. This essentially constant sensitivity is due to the inventlol'l have b96311 described With Particular feffil'ence artificially increased specific surface area of the animoammonium nitrate-fuel Oil COmPO'SitiOBS- However, nium nitrate of the present invention. Such additives the advantages of the present invention are not limited which cover a large portion of the externally available to this narrow phase of the explosives field. Thus, the

flaked ammonium nitrate of the present invention can be incorporated into substantially all ammonium nitrate explosive formulations to replace the conventionally granulated material. The types of ammonium nitrate compositions in which the present product can be used to advantage include various types of high explosives, such as ammonia gels, semi-gels, gas-producing compositions, solid propellants and the like. Because of its exceedingly great specific surface area, the present ammonium nitrate particles lend themselves particularly well to blending with the numerous components which are normally incorporated With ammonium nitrate into such compositions. Representative modifiers, accelerators, fuels and the like include nitroaromatics, such as diand trinitrotoluene; liquid nitrated esters, such as nitroglycerine and diethylene glycol dinitrate; nitrated carbohydrates, such as nitrocellulose, polyvinyl nitrate, and nitrostarch, synthetic polymeric matrices, inorganic phosphates, iron cyanide complexes, copper oxides, rosin, and the like.

The above description, and particularly the examples, are set forth by way of illustration only. Other variations and modifications can be made without departing from the spirit and scope of the invention herein described.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of preparing ammonium nitrate particles which comprises pressing in one plane prills of ammonium nitrate so as to reduce the dimensions of said prills in that plane while increasing the dimensions of a prill in a plane perpendicular, said prills having a particle density of at least about 1.5.

2. A method of forming flaked ammonium nitrate which comprises passing ammonium nitrate prills having a particle density of at least about 1.5 through a pair of rollers having a gap opening less than the diameter of the prills.

3. A disk of ammonium nitrate having a substantially solid imperforate central portion and a cohesive periphery of fractured ammonium nitrate particles.

4. A disk of ammonium nitrate having a dens ty gradient along its major axis.

5. A disk of ammonium nitrate comprising a high density central portion and a peripheral portion having a lesser density.

6. A disk of ammonium nitrate comprising a central portion with a particle density of at least about 1.6 and a peripheral portion with a particle density less than about 1.6.

7. Granular ammonium nitrate in the form of disks comprising a central portion with a particle density of at least about 1.6 and a peripheral portion with a particle density less than about 1.6, said ammonium nitrate having a bulk density less than about 55 pounds per cubic foot.

8. Particulate ammonium nitrate in the form of disks having a specific surface area of at least about one square meter per gram.

9. A disk of ammonium nitrate having a major dimension of at least about 30 mils and a specific surface area of at least about one square meter per gram.

10. A disk of ammonium nitrate having a major dimension between about 25 mils and about 500 mils and a specific surface area between about 1 and about square meters per gram.

11. As an explosive component, ammonium nitrate in the form of disks having a major dimension of at least about 30 mils and a specific surface area of at least about one square meter per gram.

References Cited by the Examiner UNITED STATES PATENTS 2,125,161 7/ 1938 Hauff et al. 149--2 2,174,238 9/1939 Gideon et a1 23103 FOREIGN PATENTS 903,614 8/1962 Great Britain. 917,577 2/1963 Great Britain.

BENJAMIN R. PADGETT, Primary Examiner.

LEON D. ROSDOL, Examiner.

L. A. SEBASTIAN, Assistant Examiner. 

1. A METHOD OF PREPARING AMMONIUM NITRATE PARTICLES WHICH COMPRISES PRESSING IN ONE PLANE PRILLS OF AMMONIUM NITRATE SO AS TO REDUCE THE DIMENSIONS OF SAID PRILLS IN THAT PLANE WHILE INCREASING THE DIMENSIONS OF A PRILL IN A PLANE PERPENDICUULAR, SAID PRILLS HAVING A PARTICLE DENSITY OF AT LEAST ABOUT 1.5.
 7. GRANULAR AMMONIUM NITRATE IN THE FORM OF DISKS COMPRISING A CENTRAL PORTION WITH A PARTICLE DENSITY OF AT LEAST ABOUT 1.6 AND A PERIPHERAL PORTION WITH A PARTICLE DENSITY LESS THAN ABOUT 1.6, SAID AMMONIUM NITRATE HAVING A BULK DENSITY LESS THAN ABOUT 55 POUNDS PER CUBIC FOOT. 